1. Field of the Invention
The invention relates to a process for the treatment of a starting mixture of liquid and solid organic wastes, which mixture is susceptible to at least partial microbiological degradation, with formation of biogas.
2. Description of Related Art
It has already been proposed (French Patent 2,541,669) to mix sludge obtained from the liquid phase of wastes by anaerobic fermentation (and optionally subsequent aerobic treatment) with the solid components intended for composting. However, this process has the disadvantage that separate thickening must be provided for relatively small amounts of sludge, or that undesirably large amounts of liquid are introduced into the composting.
Owing to its CO.sub.2 content, it has already been proposed (EP-A1-0302852) to use engine exhaust gas, possibly from the combustion of biogas, for pH reduction in intermediate stages of fermentation or rotting. In the first case, expensive fuel gas or fuel oil must be used; in the second case, the CO.sub.2 in any case present in the biogas is carried along as ballast and must be heated.